It has previously been proposed to provide a pipeline having a thermally-insulating coating by enclosing sections of foamed polyurethane within an enveloping matrix of abrasion-resistant and corrosion-resistant elastomer such as polychloroprene. This coating is very effective for use on subsea pipelines which are subject to very low temperatures and a corrosive environment. There is a need, however, for a thermally-insulating coating which meets a less rigorous specification and is less expensive and yet provides a greater degree of insulation than a continuous coating.
Such coatings of less rigorous specification are those in which one or more layers of continuous non-foamed plastics or rubber material are applied to the pipeline. This provides excellent protection for the pipeline against corrosion and mechanical damage, but the heat insulation properties of the non-foamed material are considerably inferior to those of a foamed coating. In very cold environments such as offshore in deep water good heat insulation is often essential.